Fluid container

ABSTRACT

A container for a fluid includes a rigid outer shell, an insulating layer, and at least one inner vessel, which over its surface is supported by the insulating layer. A robust and economical solution is obtained by providing that the outer shell is configured essentially as a single-piece closed container and that the insulating layer is supported by the outer shell over its surface.

The present invention relates to a container for a fluid, comprising a rigid outer shell, which essentially is configured as a single-piece closed container, and an insulating layer, which is supported over its surface by the outer shell, and at least one inner vessel, which is supported over its surface by the insulating layer.

Transporting goods in containers has gained in importance due to the simple logistics involved. This is also true for liquids and gases, that is, fluid materials transported in so-called tank containers. A conventional tank container is constructed such that an inner receptacle for receiving the fluid is disposed inside a frame of the shape of a parallelepiped, which has the standard dimensions of a container. In many cases it is required to keep the fluid at a certain temperature. To this end the inner receptacle is enclosed in an insulating layer. Applying this insulating layer is relatively expensive, and there is always the danger that the insulating layer is damaged when the container is filled or emptied, since it is freely accessible through the interstices of the frame. A further disadvantage of conventional tank containers lies in the fact that the inner receptacle must have sufficient stability in order to withstand the occurring loads. These loads consist mainly of the weight of the contents and the pressure forces exerted by interior pressure. In view of these facts conventional tank containers are heavy and expensive.

From EP 0 025 792 B there is known a tank container, which has a thin-walled inner vessel, which on its outside is enclosed by an insulating layer. The insulating layer—in addition to acting as a thermal insulator—will also help to support the inner vessel, which on its own could not sustain the load acting on it. A container of this kind will solve some of the problems mentioned and may be designed as a light-weight unit requiring little material. The critical aspect is, however, that the insulating layer must transmit the supporting forces of the inner vessel onto a frame-shaped exterior structure and must thus have relatively great strength itself. A compromise between insulating capability and mechanical strength must therefore be made when the insulating material is chosen. Moreover, manufacture of such containers is complex and expensive.

Other known solutions for improving the transport system are presented in DE 25 41 375 A, in U.S. Pat. No. 3,115,982 A, in DE 712 09 59 U, and in DE 37 02 792 A. All of these solutions are comparatively costly and provide only insufficient thermal insulation. Other known solutions are presented in DE 26 36 310 A and DE 28 56 442 A.

It is the object of the present invention to avoid the above mentioned disadvantages and to propose a container, which has a simple design, is robust and has good insulating properties while being light-weight. In particular, a great filling volume should be achieved for given exterior dimensions.

The invention achieves its object by providing that the insulating layer contains embedded vacuum insulation panels (VIPs). It is an essential aspect of the invention that a standard container can be used as exterior shell. Such containers are available in large numbers, they are series-manufactured at relatively low cost and are very robust. A further advantageous aspect of the invention lies in the fact that the insulating layer is supported by the exterior shell over its whole surface, and thus is mechanically subject only to a small pressure load. It is thus possible to select an insulating material with optimum insulating properties, as the mechanical properties are less relevant. The insulating layer is furthermore protected from mechanical damage by the exterior shell, resulting in long service life of the container. Depending on given requirements a compromise between thermal insulation and volume of the inner vessel may be found.

A further important aspect of the invention lies in the fact that no holding or fixing means will be required, which would thermally connect the inner vessel and the exterior shell, and would thus present heat bridges degrading the insulation properties.

The aim of a large filling volume is achieved in particular by reinforcing the insulating layer with vacuum insulation panels (VIPs). VIPs are extensively used where a maximum of insulation is required. Known applications of VIPs are in refrigerating equipment, mobile cooling boxes, refrigerated walls for cold-storage warehouses and refrigerated vehicles. VIPs consist of an envelope which seals against gas and water-vapour, and a filling material inside the envelope, the envelope being sealed after having been evacuated to a partial vacuum. Such vacuum insulation panels are for instance described in DE 198 14 271 A, DE 298 09 807 U, or DE 298 11 136.5 A. Usually silicic acid is used as filling material, which is pressed into a plate, which is then sealed in vacuum into a gas- and water-vapour-tight sheet.

Other known filling materials for making VIPs are glass fibres, open-cell plastic foams, silicic acid and degassed PUR-foam from recycled refrigerators. It is also known to pour loose filling material into an envelope which is then evacuated, thereby imparting stability to the panel.

Metal foils or plastic sheets or a combination of both may be used for the envelopes. Essential properties of vacuum panels and their filling materials include low thermal conductivity, pressure resistance, thermal stability, high heat capacity and constancy of shape. By using VIPs in critical areas of little wall thickness, i.e. usually in the central regions of the walls, an inner vessel with large diameter may be employed, since the required insulation can be achieved with comparatively thin walls.

Particularly simple manufacture and a very good insulation layer will be achieved if the insulation layer is essentially foamed up in situ. Only at the front ends of the inner vessel it may be of advantage if the inner vessel is kept freely accessible for maintenance work. In this context it is of special advantage if the required fittings, such as valves, filling openings, man holes etc. are located in this area so as to be freely accessible. In order to ensure a proper insulation effect suitably shaped bodies of insulating material are provided, which will complete the insulation layer in this area. Alternatively, in situ foamed insulation bodies may be provided at the front end areas, which are provided inside of foils, however, to prevent them from sticking to the container doors or fittings.

An alternative solution proposes to build up the complete insulation layer from a multitude of suitably shaped bodies. This would permit removal of the inner vessel if required, and use of the container forming the outer shell for other purposes.

A particular advantage of the solution according to the invention lies in the fact that the inner vessel need not necessarily have circular cross-section, even if it is designed as a pressure vessel. It is entirely possible and feasible to configure the inner vessel with rectangular cross-section with rounded-off corners to avoid wasted space and achieve greater volume.

Preferentially, a hollow space is provided in the region of the inner vessel, which space can be filled with a heat storing medium. Even very good insulation may not be sufficient to maintain a certain required temperature level during long transports or for critical goods. To avoid the necessity of special cooling or heating equipment a heat storing medium may be provided within the insulating layer, which helps to keep temperature within given limits. In the case of refrigerated transports ice or dry ice may be used, for transports where temperature of the goods must not fall below a certain threshold, hot water may be used as heat storing medium, or a chemical agent having a phase transition in a suitable temperature interval. A hollow space in the insulating layer may be provided for receiving the heat storing medium. It is of particular advantage, however, if the heat storing medium is contained in yet another flexible vessel, which is disposed within the insulating layer together with the inner vessel.

In the region of the doors a closable maintenance opening may be provided. This will permit access to the fittings without the need for opening the doors. The doors themselves possibly may be permanently closed, i.e. welded, since operational handling may be effected via the maintenance opening. If required, more maintenance openings may be provided at other points, for instance on the topside of the container.

The invention will now be described in more detail, with reference to the embodiment shown in the enclosed drawings. There is shown in

FIG. 1 a longitudinal section along a horizontal plane of a container according to the invention;

FIG. 2 a section along line II-II of FIG. 1; and

FIG. 3 a section along line III-III of FIG. 1.

The container of FIG. 1 comprises an outer shell 1, which is configured as a standard container. Inside the outer shell 1 there is an inner vessel 2, which is a thin-walled stainless steel tank, having a wall thickness of for instance 0.8 mm, depending on static requirements. The inner vessel 2 lies with its whole surface against an insulating layer 3, which in turn is supported by the inside of the outer shell 1. The insulating layer 3 is foamed-up in situ as one piece, and is made of polyurethane with a weight of 30-80 kg/m³. At a front end of the outer shell 1 doors 6 are provided, as is customary in containers, to permit access to the interior. In this area fittings are provided, such as valves 4 or a man hole 5. In the area between the doors 6 and the inner vessel 2 especially shaped bodies 7 of insulating material are provided to complete the insulating layer 3 in this area. A rinsing line (CIP-line) 8 is provided for cleaning the inner vessel 2.

Reference number 11 indicates an embedded vacuum insulation panel (VIP) in the region of a side wall. Analogously, such panels could be used in the other side walls or at the top or bottom. The embedded panels are provided only in regions where the insulating layer 3 has small thickness, and may be kept small if the inner vessel 2 has circular cross-section. This will result in optimum cost-effectiveness.

Within the door 6 a closable maintenance opening 10 is provided, which is used for inspection and for filling and draining.

According to FIG. 3 the inner vessel 2 does not have circular cross-section but is essentially rectangular with rounded-out corners. In this way maximum filling volume will be obtained.

The present invention permits the manufacture of tank containers, which are economical, robust and have optimum insulation effect. 

1-11. (canceled)
 12. A container for a fluid, comprising a rigid outer shell which essentially is configured in a single piece as a closed container, an insulating layer which is supported by the outer shell over its surface, and at least one inner vessel which is supported by the insulating layer over a surface thereof, wherein the insulating layer contains embedded vacuum insulation panels (VIP).
 13. The container according to claim 12, wherein the vacuum insulating panels (VIP) are located in areas of minimum thickness of the insulating layer.
 14. The container according to claim 12, wherein the insulating layer is foamed up in situ at least underneath, on top and on the sides of the inner vessel.
 15. The container according to claim 14, wherein the insulating layer is foamed up in situ inside a protective sheet at least at one front end of the inner vessel.
 16. The container according to claim 14, wherein the insulating layer comprises at least one body of rigid shape at least at one front end of the inner vessel.
 17. The container according to claim 12, wherein the insulating layer comprises a plurality of bodies of rigid shape.
 18. The container according to claim 12, wherein the inner vessel comprises fittings which are located at one front end.
 19. The container according to claim 12, wherein the inner vessel has non-circular cross-section which is adapted to a rectangular cross-section of the outer shell.
 20. The container according to claim 12, wherein the outer shell is configured as a standard container.
 21. The container according to claim 12, including at least one hollow space in a region of the inner vessel for receiving a heat storing medium.
 22. The container according to claim 12, including a closable maintenance opening in an area of the doors. 